I can't make working the heartbeat system when my ICEFaces webApplication is deployed on the root of my application server http://localhost:8080/ (on JBOSS 4.2.2)
With firebug plugin I can see unsuccess attempts every seconds wehereas it is working fine when the webapp is deployed into a subfolder like http://localhost:8080/myWebApp/
You can test it easyly by adding the following jboss-web.xml file into the WEB-INF directory of your webApp.